On the convergence of multi-level Hermite-Pad\'e approximants

In the present paper we prove a Stieltjes type theorem on the convergence of a sequence of rational functions associated with a mixed type Hermite-Pad\'e approximation problem of a Nikishin system of functions and analyze the ratio asymptotic of the corresponding Hermite-Pad\'e polynomials.Comment: 24 page

GFET Asymmetric Transfer Response Analysis through Access Region Resistances

Graphene-based devices are planned to augment the functionality of Si and III-V based technology in radio-frequency (RF) electronics. The expectations in designing graphene field-effect transistors (GFETs) with enhanced RF performance have attracted significant experimental efforts, mainly concentrated on achieving high mobility samples. However, little attention has been paid, so far, to the role of the access regions in these devices. Here, we analyse in detail, via numerical simulations, how the GFET transfer response is severely impacted by these regions, showing that they play a significant role in the asymmetric saturated behaviour commonly observed in GFETs. We also investigate how the modulation of the access region conductivity (i.e., by the influence of a back gate) and the presence of imperfections in the graphene layer (e.g., charge puddles) affects the transfer response. The analysis is extended to assess the application of GFETs for RF applications, by evaluating their cut-off frequency.This research was founded by Spanish government grant numbers TEC2017-89955-P (MINECO/AEI/FEDER, UE), TEC2015-67462-C2-1-R (MINECO), IJCI-2017-32297 (MINECO/AEI), FPU16/04043 and FPU14/02579, and the European Union’s Horizon 2020 Research and Innovation Program under Grant GrapheneCore2 785219

Morphology evolution of thermally annealed polycrystalline thin films

Investigation of the morphology evolution of annealed polycrystalline Au(111) films by atomic force microscopy and x-ray diffraction leads to a continuous model that correlates such an evolution to local interactions between grains triggering different mechanisms of stress accommodation (grain zipping and shear strain) and relaxation (gap filling and grain rotation). The model takes into consideration findings concerning the in-plane reorientation of the grains during the coalescence to provide a comprehensive picture of the grain-size dependence of the interactions (underlying the origin of the growth stress in polycrystalline systems); and in particular it sheds light on the postcoalescence compressive stress as a consequence of the kinetic limitations for the reorientation of larger surface structuresThis paper was supported by the projects F1-54173 (bilateral program CSIC-Conacyt) 200960I182 (CSIC), and CCG10-UAM/MAT-5537 (DGUI-Comunidad de Madrid and Universidad Aut´onoma deMadrid). A.G.G. acknowledges the financial support of the MICINN Spanish Ministry under the project ESP2006-14282-C02-0

The High Cadence Transit Survey (HiTS): Compilation and Characterization of Light-curve Catalogs

Indexación: Scopus.J.M. acknowledges support from CONICYT-Chile through CONICYT-PCHA/Doctorado-Nacional/2014-21140892. J.M., F.F., G.C.V., and G.M. acknowledge support from the Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to the Millennium Institute of Astrophysics (MAS). F.F. acknowledges support from Conicyt through the Fondecyt Initiation into Research project No. 11130228. J.M., F.F., J.S.M., G.C.V., and S.G. acknowledge support from Basal Project PFB-03, Centro de Modelamiento Matemáico (CMM), Universidad de Chile. P.L. acknowledges support by Fondecyt through project #1161184. G.C.V. gratefully acknowledges financial support from CON-ICYT-Chile through FONDECYT postdoctoral grant number 3160747 and CONICYT-Chile and NSF through the Programme of International Cooperation project DPI201400090. P.H. acknowledges support from FONDECYT through grant 1170305. L.G. was supported in part by the US National Science Foundation under grant AST-1311862. G.M. acknowledges support from Conicyt through CONICYT-PCHA/Magís-terNacional/2016-22162353. Support for T.d.J. has been provided by US NSF grant AST-1211916, the TABASGO Foundation, and Gary and Cynthia Bengier. R.R.M. acknowledges partial support from BASAL Project PFB-06, as well as FONDECYT project N◦1170364. Powered@NLHPC: this research was supported by the High Performance Computing infrastructure of the National Laboratory for High Performance Computing (NLHPC), PIA ECM-02, CONICYT. This project used data obtained with the Dark Energy Camera (DECam), which was constructed by the Dark Energy Survey (DES) collaborating institutions: Argonne National Lab, the University of California Santa Cruz, the University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnologi-cas-Madrid, the University of Chicago, University College London, the DES-Brazil consortium, the University of Edinburgh, ETH-Zurich, the University of Illinois at Urbana-Champaign, Institut de Ciencies de l’Espai, Institut de Fisica d’Altes Energies, Lawrence Berkeley National Lab, Ludwig-Maximilians Universitat, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Lab, Stanford University, the University of Sussex, and Texas A&M University. Funding for DES, including DECam, has been provided by the U.S. Department of Energy, National Science Foundation, Ministry of Education and Science (Spain), Science and Technology Facilities Council (UK), Higher Education Funding Council (England), National Center for Supercomputing Applications, Kavli Institute for Cosmological Physics, Financia-dora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo a Pesquisa, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia (Brazil), the German Research Foundation-sponsored cluster of excellence “Origin and Structure of the universe,” and the DES collaborating institutions. Facility: CTIO:1.5 m (DECam).The High Cadence Transient Survey (HiTS) aims to discover and study transient objects with characteristic timescales between hours and days, such as pulsating, eclipsing, and exploding stars. This survey represents a unique laboratory to explore large etendue observations from cadences of about 0.1 days and test new computational tools for the analysis of large data. This work follows a fully data science approach, from the raw data to the analysis and classification of variable sources. We compile a catalog of ∼15 million object detections and a catalog of ∼2.5 million light curves classified by variability. The typical depth of the survey is 24.2, 24.3, 24.1, and 23.8 in the u, g, r, and i bands, respectively. We classified all point-like nonmoving sources by first extracting features from their light curves and then applying a random forest classifier. For the classification, we used a training set constructed using a combination of cross-matched catalogs, visual inspection, transfer/active learning, and data augmentation. The classification model consists of several random forest classifiers organized in a hierarchical scheme. The classifier accuracy estimated on a test set is approximately 97%. In the unlabeled data, 3485 sources were classified as variables, of which 1321 were classified as periodic. Among the periodic classes, we discovered with high confidence one δ Scuti, 39 eclipsing binaries, 48 rotational variables, and 90 RR Lyrae, and for the nonperiodic classes, we discovered one cataclysmic variable, 630 QSOs, and one supernova candidate. The first data release can be accessed in the project archive of HiTS (http://astro.cmm.uchile.cl/HiTS/). © 2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/1538-3881/aadfd

General Non-equilibrium Theory of Colloid Dynamics

A non-equilibrium extension of Onsager's canonical theory of thermal fluctuations is employed to derive a self-consistent theory for the description of the statistical properties of the instantaneous local concentration profile n(r,t) of a colloidal liquid in terms of the coupled time evolution equations of its mean value n(r,t) and of the covariance {\sigma}(r,r';t) \equiv of its fluctuations {\delta}n(r, t) = n(r, t) - n(r, t). These two coarse-grained equations involve a local mobility function b(r, t) which, in its turn, is written in terms of the memory function of the two-time correlation function C(r, r' ; t, t') \equiv <{\delta}n(r, t){\delta}n(r',t')>. For given effective interactions between colloidal particles and applied external fields, the resulting self-consistent theory is aimed at describing the evolution of a strongly correlated colloidal liquid from an initial state with arbitrary mean and covariance n^0(r) and {\sigma}^0(r,r') towards its equilibrium state characterized by the equilibrium local concentration profile n^(eq)(r) and equilibrium covariance {\sigma}^(eq)(r,r'). This theory also provides a general theoretical framework to describe irreversible processes associated with dynamic arrest transitions, such as aging, and the effects of spatial heterogeneities

Procesadores de bajo coste y su aplicación en la docencia de Ingeniería de Computadores

La Informática evoluciona a gran velocidad y es necesario actualizar con frecuencia los recursos de aprendizaje para mantener el interés de los estudiantes. En la actualidad, hay una gran diversidad de plataformas de cómputo de bajo coste que son utilizadas como recursos en los estudios de Informática. Raspberry Pi y algunos modelos de Arduino (como Arduino Due), ambas basadas en procesadores ARM, son ejemplos representativos de este tipo de plataformas. Las arquitecturas ARM son ejemplos de procesadores RISC que actualmente gozan de gran popularidad por su buena relación entre potencia computacional, consumo y coste. De hecho, constituyen el núcleo de muchos de los teléfonos móviles y sistemas empotrados actuales. Al estar tan cerca de los estudiantes, el uso de este tipo de recursos en el aula representa una oportunidad para: (1) motivar a los alumnos de Bachillerato y Educación Secundaria para estudiar el Grado de Informática y (2) potenciar el interés de los alumnos de Grado de Informática por la Ingeniería de Computadores. Existe una serie de eventos consolidados que tienen una gran difusión social. En ellos, se muestran vistosos ejemplos de aplicación y funcionamiento de este tipo de plataformas. En este trabajo se describen el conjunto de sistemas interactivos y basados en plataformas computacionales de bajo coste que se han desarrollado para ser utilizadas en este tipo de eventos. De acuerdo con nuestra experiencia de participación, creemos que están sirviendo para despertar el interés del alumno de secundaria por la Informática en general, y más específicamente por la Ingeniería de Computadores. Por otra parte, un porcentaje de los alumnos que cursan el Grado de Ingeniería Informática no está interesado en el análisis de los componentes hardware y de su organización para construir un computador moderno. Piensan que la asignatura de Arquitectura de Computadores del Grado en Ingeniería Informática está lejos de su futura actividad profesional. En este contexto, nos planteamos seleccionar ARM como arquitectura de referencia para desarrollar los contenidos de la asignatura de Arquitectura de Computadores. Creemos que esta decisión mejora el interés del alumno por dos motivos: (1) el objeto de estudio se usa en multitud de plataformas muy cotidianas para el alumno y (2) es posible diseñar las actividades prácticas de las asignaturas basadas en elementos reales y no únicamente virtuales. Este trabajo muestra las distintas actividades tanto a nivel teórico como práctico que se plantean al alumno en el marco de la asignatura Arquitectura de Computadores.Computer Science is advancing rapidly and it is necessary to keep the educational resources up to date in order to keep the interest of students. Nowadays, there is a wide variety of low-cost computing platforms that are used as educational resources in the Computer Science degree. Raspberry Pi and some models of Arduino (such as Arduino Due), which are both based on ARM processors, are representative examples of this kind of platforms. ARM architectures are instances of RISC processors which nowadays have reached an important popularity due to their good relation between performance, consumption and cost. In fact, they constitute the core of numerous current mobile phones and embedded systems. Considering their proximity to the students, the use of this kind of resources in the classroom is an opportunity to: (1) encourage the high schools pupils to study the Computer Science degree and (2) to increase the interest of the students for the Computer Engineering. There are several consolidated informational events of great social outreach in which different examples of application of this kind of platforms are shown. In this work, the set of interactive systems designed to be used in this kind of events is described. According to our experience, we think that they arouse the interest of high schools pupils for the Computer Science in general, and, more specifically, for the Computer Engineering. Furthermore, a percentage of the students of the Computer Science degree is not interested in the analysis of hardware components and the architecture of modern computers. They think that the subject of Computer Architecture of the Computer Science Degree is far from his/her future career. In this context, we will select ARM as a reference architecture where the contents of the subject Computer Architecture will be developed on. We think this might improve the motivation of the students mainly for two reasons: (1) the object of study is being used in a lot of modern platforms; and (2) it is possible to design the practical activities of the subjects using real platforms and not only virtual ones. This work shows the activities proposed to the students in the context of the subject Computer Architecture, considering both practical and theoretical approaches